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Results tagged with group-cohomology
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user 5010
In mathematics, group cohomology is a set of mathematical tools used to study groups using cohomology theory, a technique from algebraic topology. Analogous to group representations, group cohomology looks at the group actions of a group G in an associated G-module M to elucidate the properties of the group.
4
votes
central extensions of Diff(S^1) and of the semigroup of annuli
Let me give a method for answering the problem. I haven't yet done the relevant integral to get an actual answer.
In the setting you originally laid out for $\mathcal{A}$, actual diffeomorphisms are …
- 10.1k
6
votes
central extensions of Diff(S^1) and of the semigroup of annuli
There's a more geometrically natural description of a $\mathbb{Z}$-central extension in both cases.
For $\operatorname{Diff}(S^1)$, the central extension are diffeomorphisms $f: \mathbb{R} \to \mathb …
- 10.1k